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Studies Of The Precambrian Geology Of Iowa: Part 3. Geochronologic Data For The Matlock Drill Holes, W. R. Van Schmus, E. T. Wallin
Studies Of The Precambrian Geology Of Iowa: Part 3. Geochronologic Data For The Matlock Drill Holes, W. R. Van Schmus, E. T. Wallin
Journal of the Iowa Academy of Science: JIAS
U-Pb ages have been determined for quartz monzodiorite (2,535 ± 5Ma) recovered from drill hole ClO and for keratophyre (1,782±10 Ma) recovered from drill hole C5 of the Matlock exploration project. Sm-Nd whole-rock analyses for several rock types from the Otter Creek layered mafic complex recovered from several drill holes of the Matlock project yield an isochron age of 2,890 ± 90 Ma, with an ϵNd(t) of -0.9 ± 2.4. These ages document crustal evolution in northwest Iowa, including the southern margin of the Superior Province, over more than one billion years from 2.9 to 1.8 Ga. Isotopic data also …
Studies Of The Precambrian Geology Of Iowa: Part 1. The Otter Creek Layered Igneous Complex, Kenneth E. Windom, Karl E. Seifert, Raymond R. Anderson
Studies Of The Precambrian Geology Of Iowa: Part 1. The Otter Creek Layered Igneous Complex, Kenneth E. Windom, Karl E. Seifert, Raymond R. Anderson
Journal of the Iowa Academy of Science: JIAS
Rocks from a buried igneous body, herein called the Otter Creek layered igneous complex, were recovered by drilling in Archean rocks in northwestern Iowa. This complex consists of layers of ultramafic and mafic cumulate rocks, including bronzitite, harzburgite, dunite, gabbro, and anorthosite. These rocks have been subjected to low-grade metamorphism with a patagenesis including serpentine, chlorite, talc, uralitic amphiboles, magnetite, albite, epidote, sericite, and minor quartz and calcite. During its intrusion, the magma which gave rise to the layered body engulfed a large block of rock consisting of banded iron formation and thin lamprophyre dikes. Both the iron formation and …